Components of electric machines, such as stators and rotors, are known that comprise electric bar conductors bent and variously connected together so as to make so-called bar windings.
In particular, the state of the art includes bar windings made through electric bar conductors having an essentially rectangular cross section, where by rectangular we mean both the square section and the “flat” section with which a rectangular-shaped section in which one of the two sides of the section is shorter than the other is generally indicated.
The aforementioned bar conductors are preformed usually through bending in a ‘U’ or ‘P’ shape from straight bar conductors. U.S. Pat. No. 7,480,987 describes an example of a method for preforming bar conductors (known in such a document as “hairpin conductors”). The preforming is such as to modify the shape of the straight conductors so that they can be suitably inserted in suitable radially aligned pockets made in a twisting device suitable for deforming the aforementioned preformed conductors after insertion. In practice, the twisting device is used essentially to “spread apart” the legs of the “U” or “P” shape to ensure that two legs of the same conductor, after having extracted it from the twisting device, can subsequently be inserted into the slots of a stator or rotor core radially offset from one another by a predetermined pitch.
The United States patent application published with number US 2009/0178270 describes a method for twisting preformed bar conductors after their insertion in the pockets of a twisting device.
In order to precisely bend the bar conductors that form a bar winding, there is a great need to stably clamp in position at least some of the aforementioned bar conductors after their insertion in the pockets of the twisting device, for example during the twisting operation. In particular, without for this reason introducing any limitation, there is an especially great need to stably clamp in position at least the bar conductors provided to make the so-called special elements after their insertion in the pockets of the twisting device, for example before the start of the twisting operation and for the entire duration of such an operation.